U.S. Pat. No. 5,735,387 discloses a sample processing apparatus for suctioning a sample from a sample container retained in a sample rack and processing the suctioned sample. This conventional sample processing apparatus is provided with a transport unit for transporting a sample rack holding sample containers to a sample suctioning position. The transport unit has an input region, a process region, and an output region, wherein a sample rack having a structure capable of holding a plurality of sample containers is set in the input region. The sample rack set in the input region is transported toward the suctioning position in front of a sample processing unit to enter the process region. Then, a sample of the sample container retained in the sample rack is suctioned at the sample suctioning position on the process region. The sample rack stays on the process region until a processing result is obtained by the sample processing unit. After the processing result is obtained from all of the sample containers retained in the sample rack, the sample rack is transported from the process region to the output region.
In this sample processing apparatus, the process region is encompassed by a protective housing to prevent a user from easily accessing the sample container after the sample container is transported from the input region to the process region. According to such a structure, once the sample containers are placed in the process region, the user is unable to change the arrangement and positional order of the sample containers.
In the case where a certain transport suspension event occurs during the sample processing operation, the above sample processing apparatus stops the processing operation by the sample processing unit and the transport operation by the transport unit. In this case, the processing operation by the sample processing unit and the transport operation by the transport unit restart after the suspension event is resolved. When restarting the operations, the user may have to return the sample rack currently on a transport path to the input region.
However, when the process region is covered with the protective housing as described above, the user cannot easily access the sample rack placed in the process region. Thus, it is difficult to obtain the sample rack in the case where the sample rack is located in the process region when the transport operation by the transport unit is suspended. This causes a problem in that the user has to go through some time-consuming steps to remove the sample rack from the process region.